Secure communication session setup

A method, comprising:

• transmitting a register message to a voice over internet protocol (VoIP) server;
• receiving a public key associated with the VoIP server in response to the register message;
• generating a key generating value;
• encrypting the key generating value using the public key associated with the VoIP server;
• transmitting the encrypted key generating value to the VoIP server;
• generating a temporary session key based on the key generating value;
• performing one of:
• transmitting a session invitation message designating a called party device to the VoIP server;
• or
• receiving a session invitation message designating a calling party device from the VoIP server;
• receiving an encrypted master session key;
• decrypting the encrypted master session key using the temporary session key;
• and
• using the decrypted master session key to secure a communication session with the called party device or the calling party device.

A system, comprising:

• a registration/proxy server connected to a first real time communication session device and a second real time communication session device,
• wherein the registration/proxy server is configured to:
• receive an encrypted first key generating value from the first real time communication session device;
• decrypt the encrypted first key generating value;
• generate a first temporary session key based on the first key generating value;
• receive a secure session invitation message;
• generate the master session key;
• encrypt the master session key based on the first temporary session key;
• and
• transmit the encrypted master session key based on the first temporary session key to the first real time communication session device.

A method, comprising:

• receiving a session invitation message from a first client device, the session invitation message including an encrypted first random session key in a header of the session invitation message;
• forwarding the session invitation message to a second client device;
• receiving a session acceptance message from the second client device, the session acceptance message including an encrypted second random session key in a header of the session acceptance message;
• generating a master session key;
• encrypting the master session key using the first random session key;
• modifying the header of the received session acceptance message to include the master session key encrypted using the first random session key;
• transmitting the modified session acceptance message to the first client device;
• receiving a session acknowledgement message from the first client device;
• encrypting the master session key using the second random session key;
• modifying a header of the received session acknowledgement message to include the master session key encrypted using the second random session key;
• and
• transmitting the modified session acknowledgement message to the second client device.